Twidroyd -
Official Twitter client
Where/Poynt - Google Maps (the redundancies are incredible between those three, and they all come with the phone)
Virgin Mobile Live -
TuneIn Radio, has just about every station you could want, including the Virgin one (not half bad, actually)
AirG - It's just a shortcut to a lame mobile chat/date service, forget it.
Downloads -
Zedge, tons of free ringtones. You can also make your own with
Ringdroid
My Account -
Minutes Checker for Virgin Mobile. For topups and account changes, I find it easier to just call *VM.
SCVNGR -
Foursquare or Latitude (built into Google Maps), I prefer latitude myself
Am I missing any?